1. Field of the Invention
The present invention relates to an organic electroluminescent element (hereinafter sometimes referred to as an “organic EL element”, a “light-emitting element” or an “EL element”) capable of emitting light by converting electric energy into light.
2. Description of the Related Art
Today, research and development for various display devices is being aggressively conducted and, in particular, organic electroluminescent (EL) elements are attracting attention as promising display devices because high brightness light can be emitted with a low voltage. A technique of using a plurality of compounds for the host material of the light-emitting layer and using each compound as an electron transporting host or a hole transporting host, thereby realizing reduction of power consumption and enhancement of driving durability, has been disclosed (see, for example, Japanese Patent Application Laid-Open (JP-A) Nos. 2002-313583 and 2002-324673, the disclosures of which are incorporated by reference herein). In these techniques, carriers injected into the light-emitting layer are trapped by a luminescent dopant and recombined to emit light and a high emission efficiency is obtained.
However, in such a method, since carriers are trapped by a luminescent dopant, the luminescent dopant inevitably deteriorates due to the carrier and therefore, sufficiently high driving durability cannot be easily obtained.